On the go and no time to finish that story right now? Your News is the place for you to save content to read later from any device. Register with us and content you save will appear here so you can access them to read later.

An estimated 150 people took to the streets of Whangarei for a rally against the contentious Trans Pacific Partnership trade agreement (TPPA).

Rally organiser Benjamin Pittman said the group who rallied at the Town Basin on Saturday afternoon joined thousands around the country protesting the TPPA.

He said the day of action was a chance for people to stand up for New Zealand's right to determine its own future, in a national day of action against the TPPA that is largely being negotiated in secret, with few details being made public.

Prime Minister John Key said despite the secrecy, the TPPA could bring millions of dollars of benefits to New Zealand, but Dr Pittman said he and many others believe that the only people to benefit would be big business and multi-national corporations.

"I see the TPPA as an absolute affront and insult to the founding principles of partnership. The overt secrecy with which its planning has been conducted and its threat to democracy in Aotearoa galvanised me into action. Arrogant, ignorant, self-centred government is bad news," he said.

"What we are seeing here is a complete overriding of our sovereignty ... the Treaty of Waitangi will be completely overwhelmed and consigned to history by this agreement and our sovereignty will be surrendered to corporate interests from overseas."

Some opponents of the TPPA are worried about the price of medicines. Others about the impacts on local libraries.

Dr Pittman said Maori were battling to uphold their Treaty rights against foreign mining companies, while city councillors and unions fear that more local jobs may go and workshops close as government buys offshore.

The day of action was co-ordinated by It's Our Future, and was supported by the Green, New Zealand First, Maori and Mana parties. Formal sponsors included Oxfam, Greenpeace and the Council of Trade Unions and Dr Pittman said more action against the TPPA will be held in Northland.